#include <iostream>
#include <string>
#include <map>
#include <vector>
using namespace std;
typedef long long int lint;
lint factorial(lint x){
    lint ans=1;
    for(int i=1; i<=x;++i){
        ans*=i;
        ans = ans%998244353;
    }
    return ans;
}
int main() {
    lint n;
    cin >> n;
    map<lint,map<lint,lint>> body1;
    map<lint,lint> body1_size;
    map<lint,map<lint,lint>> body2;
    map<lint,lint> body2_size;
    for(lint i=0; i<n;++i){
        lint mm,m;
        cin>>mm>>m;
        body1[mm][m]++;
        body2[m][mm]++;
        body1_size[mm]++;
        body2_size[m]++;
    }

    lint ans1=1;
    lint ans2=1;
    lint ans12=1;
    lint prmax = -1;
    bool oversort = true;
    for(auto& x:body1){
        int curmax = x.second.begin()->first;
        if(oversort && (curmax < prmax)){
            oversort = false;
        }else{
            prmax = curmax;
        }
        for(auto& y:x.second){
            ans12 = ans12*factorial(y.second);
            ans12 = ans12%998244353;
        }
    }
    for(auto& x:body1_size){
        ans1 = ans1*factorial(x.second);
        ans1 = ans1%998244353;
    }
    for(auto& x:body2_size){
        ans2 = ans2*factorial(x.second);
        ans2 = ans2%998244353;
    }
    lint xxx = (factorial(n)%998244353+lint(998244353)*3-ans1-ans2)%998244353;
    if(oversort){
        xxx+=ans12;
        xxx=xxx%998244353;
    }
    cout<< xxx <<endl;
}